Palladium catalyzed hydrogenation of bio-oils and organic compounds

ABSTRACT

The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/759,075, filed Jun. 6, 2007 now U.S. Pat. No. 7,425,657.

GOVERNMENT RIGHTS

This invention was made with Government support under ContractDE-AC0676RL01830 awarded by the U.S. Department of Energy. TheGovernment has certain rights in the invention.

FIELD OF THE INVENTION

The invention relates to methods of hydrodeoxygenation of bio-oils.

INTRODUCTION

Early work on the catalytic hydroprocessing of bio-oil (product liquidsfrom fast pyrolysis of biomass) focused on fuel production, with initialstudies aimed at complete hydrodeoxygenation (HDO) to produce fuelscompatible with existing petroleum products. Subsequent work involvedthe development of low-severity hydrogenation to produce a morethermally stable, but not entirely deoxygenated, fuel. These effortsproduced useful information relative to the thermal stability of bio-oilin processing systems, the limitations in high-temperature processing ofbio-oil, and the requirements for producing fuels from bio-oil bycatalytic hydrogenation.

The early HDO results showed that the process operated in conventionalpetroleum hydrotreaters needed to be modified for bio-oil^(i). Forexample, a low-temperature stabilization step was required beforefinishing the HDO at conventional higher temperature^(ii). Without thelow-temperature step, direct high-temperature catalytic processingresulted in high levels of char/coke production that plugged thecatalyst bed without production of liquid hydrocarbon fuels. It wasconcluded that the thermal instability of the bio-oil, as produced infast pyrolysis, led to decomposition and polymerization more rapidlythan the catalytic hydrogenation could cause the conversion to lighthydrocarbon liquid fuels. Also, while conventional alumina supportedcobalt-molybdenum and nickel-molybedenum catalysts were useful for HDOin the sulfided form^(iii,iv), i.e., high yields of hydrocarbon oilproduct could be produced without fully saturating the aromatic rings,the instability of the alumina supports in the presence of the highlevels of water was recognized as a shortcoming^(v). In addition, a highlevel of coking was identified, and carbon supports were evaluated as areplacement for alumina^(vi). ^(i) Elliott, D. C., & Baker, E. G. (1987)Hydrotreating biomass liquids to produce hydrocarbon fuels, In: Energyfrom Biomass and Waste X. (Ed. D. L. Klass), pp. 765-784. Institute ofGas Technology, Chicago.^(ii) Elliott, D. C., & Baker, E. G. (1989)Process for upgrading biomass pyrolyzates. U.S. Pat. No.4,795,841.^(iii) Baker, E. G., & Elliott, D. C. (1988) Catalyticupgrading of biomass pyrolysis oils, In: Research in ThermochemicalBiomass Conversion, (Eds. A. V. Bridgwater & J. L. Kuester), pp.883-895, Elsevier Applied Science, London.^(iv) Baldauf, W., & Balfanz,U. (1992) Upgrading of Pyrolysis Oils from Biomass in Existing RefineryStructures, VEBA OEL AG, Gelsenkirchen. Final Report JOUB-0015.^(v)Laurent, E.; (1993) Etude et contrôle des réactionsd'hydrodésoxygénation lors de l'hydroraffinage des huiles de pyrolyse dela biomasse. D.Sci. thesis, Universite Catholique de Louvain,Louvain-1a-Neuve, Belgium.^(vi) Centeno, A.; David, A.; Vanbellinghen,Ch.; Maggi, R.; Delmon, B.; (1997) Behavior of catalysts supported oncarbon in hydrodeoxygenation reactions, In: Developments inThermochemical Biomass Conversion, (Eds. A. V. Bridgwater & D. G. B.Boocock), pp. 589-601, Blackie Academic and Scientific, London.

Experimental results from hydrotreating bio-oil in the presence ofmetallic catalysts have been reported. Some batch reactor results withpalladium, copper chromite and nickel catalysts have beenreported^(vii,viii). In those tests, operation at 20° C. caused slightchanges, while tests at 100° C. resulted in what were described as“drastic changes.” Various ketones were reacted, but acetic acid was notreduced. Although gas chromatographic separations were performed on theproducts, detailed chemical conversion conclusions were not reported.^(vii) Meier, D.; Wehlte, S.; Wulzinger, P.; Faix, O. (1996) Upgradingof Bio-oils and flash pyrolysis of CCB-treated wood waste. In: Bio-OilProduction and Utilization, (Eds. A. V. Bridgwater & E. N. Hogan), pp.102-112, CPL Scientific Ltd, Newbury, UK.^(viii) Meier, D.; Bridgwater,A. V.; DiBlasi, C.; Prins, W. (1997) Integrated chemicals and fuelsrecovery from pyrolysis liquids generated by ablative pyrolysis. In:Biomass Gasification and Pyrolysis: State of the Art and FutureProspects, (Eds. M. Kaltschmitt & A. V. Bridgwater), pp. 516-527, CPLScientific Ltd, Newbury, UK.

Hydrogenation of fast pyrolysis oil was also studied by Scholze^(ix)using a batch reactor with various metal catalysts and without catalystat low temperatures. She concluded that reaction temperatures above 80°C. are unsuitable for hydrogenation of bio-oils because the productphases separate. Further, none of the combinations of bio-oils,catalysts, and conditions, which were tested, resulted in a more stableoil. She found that palladium was essentially inactive at 60° C. Raneynickel at 80° C. resulted in reduced viscosity over time (without phaseseparation), while copper chromite at the same temperature resulted in aslightly more viscous oil over time. Nickel metal was tested attemperatures from 22° C. to 100° C. At 22° C. there was noticeablereduction in carbonyl (˜15%) without noticeable change in physicalproperties. At 82° C. and 100° C. the product oil separated into twophases (as did the copper chromite catalyzed product). Chemical analysisof these products was performed to a limited degree, but little wasconcluded about the changes in the oil composition. Carbonyl analysisshowed no change in the palladium catalyzed tests and up to a 20%reduction at the intermediate temperatures of 50° C. with nickel metalcatalyst. Although gas chromatographic separations were performed on theproducts, detailed chemical conversion conclusions were not reported.^(ix) Scholze, B. (2002) Long-term stability, catalytic upgrading, andapplication of pyrolysis oils—Improving the properties of a potentialsubstitute for fossil fuels. doctoral dissertation, University ofHamburg, Hamburg, Germany.

Our earlier results with the ruthenium catalyst also included some modelcompound studies^(x). In that work, the conversion of substitutedguaiacols (4-alkyl-2-methoxyphenols) through substitutedmethoxycyclohexanols to substituted cyclohexanediols at low temperatureand substituted cyclohexanols at higher temperature was identified. Bothacetol (1-hydroxy-2-propanone), and 3-methyl-4-cyclopenten-1-one werereadily hydrogenated to propylene glycol and methylcyclopentanol,respectively. The furfural was hydrogenated through several steps to thestable form as tetrahydrofuran-methanol, with only minor evidence offurther hydrogenation. ^(x) Elliott, D. C.; Neuenschwander, G. G.; Hart,T. R.; Hu, J.; Solana, A. E.; Cao, C. “Hydrogenation of bio-oil forchemical and fuel production.” In: Proceedings of Science in Thermal andChemical Biomass Conversion Conference, Victoria, BC CANADA, August30-Sep. 4, 2004.

SUMMARY OF THE INVENTION

The invention provides a method of hydrodeoxygenation of bio-oil,comprising: providing a bio-oil and hydrogen (H2); and reacting thebio-oil and hydrogen over a catalyst at a temperature of more than 200°C. The catalyst comprises Pd. In this method, an oil, which is a liquidat room temperature, is produced from the reaction of the bio-oil andhydrogen. The term “liquid oil” means an oil that is a liquid at roomtemperature.

Typically, this method is conducted in presence of water; the bio-oiltypically comprises 5 to 50 mass % water. The bio-oil can be a singlephase or multiphase liquid. In preferred embodiments, water is removedduring the step of reacting the bio-oil and hydrogen over a catalyst.Preferably, the method is characterized by a bio-oil deoxygenation of atleast 50% and/or a yield of liquid oil of at least 60%. In preferredembodiments, the bio-oil comprises acetic acid and at least 30% of theacetic acid in the bio-oil is converted to ethanol.

The invention also includes product mixtures made from the inventivemethods.

In a further aspect, the invention provides a method of hydrogenatingfurfural, guaiacol or a substituted guaiacol, comprising: providing aliquid comprising furfural, guaiacol or a substituted guaiacol;providing hydrogen (H2); and reacting the furfural, guaiacol or asubstituted guaiacol with hydrogen over a catalyst at a temperature ofmore than 200° C. The catalyst comprises Pd. In this method, thefurfural, guaiacol or substituted guaiacol is converted to ahydrogenated product. The furfural, guaiacol or a substituted guaiacolcan be present in a bio-oil or in any other composition.

In some embodiments of hydrogenating furfural, the method is carried outat a temperature of at least 280° C., and at least 5% of the furfural isconverted to 1-pentanol. In some embodiments, at least 6% of thefurfural is converted to 2-methyl-tetrahydrofuran; preferably at atemperature of about 250 to about 300° C.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 Guaiacol Hydrogenation over Ruthenium at 150 C

FIG. 2 Guaiacol Hydrogenation over Ruthenium at 200 C

FIG. 3 Guaiacol Hydrogenation over Ruthenium at 250 C

FIG. 4 Acetic Acid Hydrogenation over Ruthenium at 150 C

FIG. 5 Acetic Acid Hydrogenation over Ruthenium at 200 C

FIG. 6 Acetic Acid Hydrogenation over Ruthenium at 250 C

FIG. 7 Cyclic Ether Products from Furfural Conversion over Ruthenium at150 C

FIG. 8 Cyclic Ketone Products from Furfural Conversion over Ruthenium at150 C

FIG. 9 Cyclic Ether Products from Furfural Conversion over Ruthenium at200 C

FIG. 10 Cyclic Ketone Products from Furfural Conversion over Rutheniumat 200 C

FIG. 11 Cyclic Ether Products from Furfural Conversion over Ruthenium at250 C

FIG. 12 Cyclic Ketone Products from Furfural Conversion over Rutheniumat 250 C

FIG. 13 Guaiacol Hydrogenation over Palladium at 200 C

FIG. 14 Guaiacol Hydrogenation over Palladium at 250 C

FIG. 15 Guaiacol Hydrogenation over Palladium at 300 C

FIG. 16 Acetic Acid Conversion over Palladium at 200 C

FIG. 17 Acetic Acid Conversion over Palladium at 250 C

FIG. 18 Acetic Acid Conversion over Palladium at 300 C

FIG. 19 Cyclic Ether Products from Furfural Conversion over Palladium at200 C

FIG. 20 cyclic Ketone Products from Furfural Conversion over Palladiumat 200 C

FIG. 21 Cyclic Ether Products from Furfural Conversion over Palladium at250 C

FIG. 22 Cyclic Ketone Products from Furfural Conversion over Palladiumat 250 C

FIG. 23 Cyclic Ether Products from Furfural Conversion over Palladium at300 C

FIG. 24 Cyclic Ketone Products from Furfural Conversion over Palladiumat 300 C

DETAILED DESCRIPTION OF THE INVENTION

Bio-oil (product liquids from fast pyrolysis of biomass) is a complexmixture of compounds derived from the thermal breakdown of thebio-polymers in biomass. In the case of lignocellulosic biomass, thestructures of three major components, cellulose, hemicellulose andlignin, are well represented by the bio-oil components. In order tostudy the chemical mechanisms of catalytic hydroprocessing of bio-oil,three model compounds were chosen to represent those components. A largenumber of mono- and di-methoxy phenols are typically found in bio-oilderived from softwood or hardwood, respectively. Guaiacol was used torepresent the mono- and di-methoxy phenols found in bio-oil. A majorpyrolysis product group from cellulosics includes furfural and similarcompounds. Acetic acid is a major product from biomass pyrolysis, whichhas important impacts on the further processing of the bio-oil becauseof its acidic character. These three compounds were processed usingpalladium or ruthenium catalyst over a temperature range from 150° C. to350° C. The batch reactor was sampled during each test over a period offour hours. The samples were analyzed by gas chromatography with both amass selective detector and a flame ionization detector. The productswere determined and the reaction pathways for their formation aresuggested based on these results. Both temperature and catalyst metalhave significant effects on the product composition.

Catalyst

The catalyst in the inventive methods should contain sufficientpalladium to sustain a significant level of activity under the selectedreaction conditions. Preferably the catalyst contains at least 0.1% Pd(throughout this description, % indicates weight % unless otherwisespecified, with weight % Pd is calculated based on the weight of a wallcoating or catalyst pellet or other configuration that includes theweight of catalyst support but not the weight of the chemical reactoritself. More preferably, the catalyst comprises at least 1 weight % Pd,and in some embodiments the catalyst comprises 2 to 5 weight % Pd. Inaddition to Pd, other metals may be present. In preferred embodiments,the catalyst metal consists essentially of Pd (without other metals thatsubstantially affect the process), or consists of Pd (without othermetals). Pd metal has been found to be stable in this processingenvironment despite the relatively high level of water and oxygenatedmaterials.

Preferably, Pd metal particles are dispersed on a support. The supportsshould be stable to the reaction conditions. Preferred supports arecarbon, titania (preferably rutile), and zirconia (preferably themonoclinic form). Activated carbon is a well-known high-surface area(typically ˜1000 m²/g) support material which has been shown to bestable in hot water processing environments; rutile titania andmonoclinic zirconia have lesser surface area (typically 30-80 m²/g) andhave demonstrated utility for catalytic metal support and use in the hotwater processing environment (see U.S. Pat. Nos. 5,616,154; 6,235,797incorporated herein as if reproduced in full below).

Reactants

Bio-oils are a complex mixture of compounds, including oxygenates, thatare obtained from the breakdown of bio-polymers. Bio-oils can be derivedfrom plants such as grasses and trees, and other sources ofligno-cellulosic material, such as derived from municipal waste, foodprocessing wastes, forestry wastes and pulp and paper byproducts.Starting materials of the present invention typically include water,typically at least 5 mass % water in a liquid, in some embodiments atleast 10% or at least 20% water. In some embodiments there is 5 to 50mass % water, in some embodiments 10 to 40 mass %. In some embodimentsup to 35%. The water may be present in a single phase with the oil, orprimarily in a second phase (for an example an emulsion with the aqueousphase as either the major or minor component), or in mixture of phases.In some preferred embodiments, a second (primarily) water phase isformed during a hydrogenation reaction and is removed during or afterthe hydrogenation treatment.

Hydrogen can be added separately or together with the bio-oil into areactor. In the case of a continuous process, hydrogen can be addedalong the length of a reactor. The hydrogen is preferably added inexcess of stoichiometry to maximize reaction rate by minimizing masstransfer limitations. In our testing, typical hydrogen feed to thereactor is 10,000 standard cubic feet (SCF) of hydrogen per barrel (bbl)of oil feed (1781 liter/liter) and overall testing from 5500 to 18300SCF/bbl.

Preferably, hydrogen is reacted with the bio-oil feedstock at a level ofat least 50 liter/liter, more preferably at least 100 liter/liter, andstill more preferably at least 200 liter/liter, in some embodiments inthe range of 100 to 300 liter/liter, and in some embodiments in therange of 100 to 175 liter/liter. Excess hydrogen may be recycled into areactor.

Reactor Configuration

Apparatus for conducting the inventive processes is not limited. Theprocesses can be conducted batchwise or continuously. The catalyst canbe present as a wall coating, fluidized bed, fixed bed of particles orpellets, etc. A fixed bed of catalyst particles has the advantage ofease of design and operation (clean-up and catalyst replacement). Insome embodiments, fluidized bed reactors may be preferred, especially ifthe bio-oil is contaminated with inorganic material. In someembodiments, wall coated reactors, which have certain advantages forheat and mass transfer, may be preferred.

Operating Conditions

The inventive processes are carried out at temperatures greater than200° C., more preferably in the range of 220 to 500° C., in someembodiments at least about 250° C. or at least about 300° C.; in someembodiments in the range of 240° C. or about 250° C. to 450° C., or 400°C., or 350° C., or about 300° C.

The reactions are carried out under pressure. Preferably, the processesare carried out at pressures of at least 1 MPa, more preferably at least5 MPa, in some embodiments at least 10 MPa, in some embodiments pressureis in the range of 1 MPa to 25 MPa.

Preferably, bio-oils are not preheated prior to the hydrogenation sinceprolonged heating or storage at elevated temperatures can causedegradation. Similarly, in preferred embodiments the products arequickly cooled after hydrogenation.

For continuous processing, the process desirably has as high a liquidhourly space velocity (LHSV) as possible. LHSV is based on the liquidvolume of feedstock (including water) at standard temperature andpressure that is fed into a reactor. The reactor volume used forcalculating LHSV is the volume where catalyst is present (in the case ofa wall coating, it includes the volume of the flow path past thecatalyst wall coating). LHSV (in volume per volume per hour) ispreferably at least 0.01, more preferably at least 0.1, and in someembodiments about 0.05 to about 0.25.

In view of the descriptions herein, for any given bio-oil (includingbio-oil derived) feedstock, conditions can be controlled to produce aset level of reactant conversion and/or product yield. The inventivemethods can be defined to include any of the conversions and/or yieldsfrom the Examples. Due to the complexity of bio-oils, this can be thebest way (indeed the only way) to define certain aspects of theinvention. For example, the product is preferably at least 40%deoxygenated, more preferably at least 50% deoxygenated, and in someembodiments is about 50% to about 65% deoxygenated. “Deoxygenation” ismeasured on a dry basis (excluding water) and is based on the reductionof the mass % of oxygen in the oil. The yield of oil (defined on a drybasis, excluding water) is preferably at least 60%, more preferably 75%,and in some embodiments is up to about 83%. The yield and %deoxygenation are properties of the inventive methods. The term “oil” isdefined to mean a substance that is a liquid at room temperature anddoes not include water (although water is sometimes dissolved orsuspended with oil).

Guaiacol is 2-methoxy-phenol. Substituted guaiacols are 2-methoxy-phenolwith alkyl substituents (having up to 6 carbons), such as propyl,methyl, and ethyl, in the 4-position. In some preferred embodiments ofthe invention, at least about 50% (in some embodiments at least about60%) of guaiacol in a starting feedstock is converted to2-methoxycyclohexanol, or at least about 50% (in some embodiments atleast about 60%) of substituted guaiacol in a starting feedstock areconverted to cyclohexanol derivatives (compounds that include acyclohexanol moiety). In some embodiments, about 50% to about 80% ofguaiacol and/or substituted guaiacols are converted to 2-methoxy-phenolor other cyclohexanol derivatives. In a preferred embodiment, thisreaction takes place at a temperature of at least about 250° C., in someembodiments in the range of about 240° C. to about 270° C.

In some preferred embodiments, at least about 50% of acetic acid in afeedstock is consumed in a hydrogenation treatment; in some embodimentsabout 50% to about 65% is consumed. In some preferred embodiments, atleast about 30% of acetic acid is converted to ethanol, in someembodiments about 30% to about 40% of acetic acid is converted toethanol.

Preferably, at least 90%, more preferably at least 99% of furfural isconsumed in the hydrogenation treatment. In some preferred embodiments,at least about 5% of the furfural is converted to 1-pentanol, in someembodiments about 5% to about 9% of furfural is converted to 1-pentanol;preferably at temperatures of at least about 280° C., in someembodiments about 280° C. to about 350° C. In some preferredembodiments, at least about 6% of the furfural is converted to2-methyl-tetrahydrofuran (mTHF), in some embodiments about 6% to about10% of furfural is converted to m-thf; preferably at temperatures of atleast about 250° C., in some embodiments about 250° C. to about 300° C.

To test conversion percentages in processing a bio-oil, a small amountof labeled compound can be injected into a feed stream and the productstream can be analyzed for labeled compounds.

Products

The invention also includes product mixtures, especially productmixtures that are produced by the processes of the invention. Theinvention includes fuels made by the inventive processes. Productsmixtures made by the inventive processes are unique mixtures that haveone or more advantageous properties such as desirable combustionproperties and high proportions of desirable chemical products such asethanol and/or 2-methylcyclohexanol.

The products resulting from the hydrogenation treatment can be usedwithout further treatment. More preferably, the product resulting fromthe hydrogenation treatment is further treated by additional processessuch as: water removal, separation of one or more chemical components,and additional hydrogenation or other fuel processing treatment.

Results of Testing—Catalysts and Conditions

As described in the examples, three chemical models were reacted at 150,200, 250, and 300° C. using either the palladium or the rutheniumcatalyst. The products varied with temperature and the catalyst metal.The experimental product from the catalyzed tests contained about 30components of sufficient concentration to be identified and quantified.This level of complexity can be compared to whole hydrogenated bio-oil,which typically contains hundreds of components. The components wereseparated into four groups to represent the products from acetic acid,guaiacol and two collections of products from furfural.

Ruthenium Catalyzed Hydrogenations. For guaiacol hydrogenation in thepresence of ruthenium catalyst the products were similar to thoseidentified earlier in our laboratory. At 150° C., 54% of the guaiacolhad already been converted by the time the reactor reached temperature,time zero in FIG. 1. The primary product was that resulting fromsaturation of the phenolic ring, 2-methoxycyclohexanol (40% yield @ 1h). Cyclohexanediol was the secondary product (8%), althoughcyclohexanol was also significant (4%). The methanol byproduct was found(1%). There was little phenol formed at this temperature. At 200° C. theinitial conversion of guaiacol during heatup was 62%. As shown in FIG. 2the methoxycyclohexanols were still the main product (38% yield @ 4 h),but cyclohexanediol became less important (3%) while more cyclohexanolwas formed (8%). More methanol was present (2%), as was more phenol. At250° C., 60% of the guaiacol was converted by the time the reactorreached temperature. As shown in FIG. 3 cyclohexanol almost surpassedmethoxycyclohexanols as the main product. Methoxycyclohexanol yieldpeaked at 17% in the 1 to 2 h range before reacting on to secondaryproducts. The maximum cyclohexanol yield was 13%. Cyclohexanediol wasonly a minor product (1%). More phenol was evident and cyclohexanebecame a significant product (2%); however, the hexane recovery islikely limited by its low solubility in the water. More cyclohexane mayhave been actually produced and remained in the reactor as a separatelight phase, which could not be sampled by our method. Over the periodof the test, the amount of aqueous phase products is reduced. A largemethane gas product was produced in this test, as has been reported forprocessing at these conditions of temperature and catalyst whereinphenol was extensively gasified at as low as 250° C.^(xi). At 300° C.,phenol is the primary product that was recoverable. Cyclohexanol andmethoxycyclohexanol are early products which are reduced to low levelswithin the first hour at temperature. All three isomers of methyl-phenol(cresols) are significant byproducts, as is benzene. Cyclohexane ispresent in the water product only at low concentration, but is likelypresent as a significant product in a separate phase. Because of thelarge amount of methane gas formation, this test was hydrogen limitedwith the reactor pressure surpassing the pressure set point after 1 h ofoperation and this factor is expected to have skewed the mechanism awayfrom the high-use hydrogenation pathways, such as saturation of thearomatic ring. ^(xi) Elliott, D. C.; Hart, T. R.; Neuenschwander, G. G.“Chemical Processing in High-Pressure Aqueous Environments. 8. ImprovedCatalysts for Hydrothermal Gasification.” Ind. Eng. Chem. Res. 45(11)3776-81, 2006.

The products from acetic acid were determined to be much more limited.Ethanol and ethyl acetate were attributed to hydrogenation of aceticacid. At 150° C. (see FIG. 4) there was only a small amount of ethanolformed (2%) with 85% of the acetic acid unreacted. Even at 200° C.(shown in FIG. 5) the ethanol yield was minimal (3%) while 84% of theacetic acid remained. However, at 250° C. there was strong evidence ofreaction with 96% of the acetic acid converted as shown in FIG. 6. Theethanol product was formed with a maximum yield of 32% at 2 h and thenwas reacted further with only 8% remaining after 4 h. Ethyl acetateformation was not significant. A large methane product appeared to bethe final product from acetic acid under these conditions, as it and theethanol were nearly gone by the end of the test. This result is notsurprising with the ruthenium catalyst, as has been found in otherprocess development work on catalytic wet gasification at ourlaboratory^(xii). At 300° C. in this batch test mode, the acetic acidconversion to ethanol was actually less, apparently because of thehydrogen limitation and the large amount of gas (methane and carbondioxide) formation. ^(xii) Elliott, D. C.; Neuenschwander, G. G.; Hart,T. R. Low-Temperature Catalytic Gasification of Chemical ManufacturingWastewaters: 1995-1998 Final Report. PNNL-11992, Pacific NorthwestNational Laboratory, Richland, Wash. 1998.

Furfural reacted quickly over the temperature range from 150 to 250° C.At 150° C., 83% of furfural was converted during heat-up to temperature.As shown in FIG. 7, the major product at 150° C. wastetrahydrofuran-methanol (THF-MeOH) at 8% with a lesser amount ofγ-valerolactone (GVL) at 4%. 1,4-pentanediol (14PDO) was a lesserintermediate that was converted further to2-methyl-tetrahydrofuran^(xiii) (MTHF) with <1% remaining. Thedemethylated versions, γ-butyrolactone (GBL) and tetrahydrofuran (THF),were also found, as was 1,2-pentanediol (12PDO). As seen in FIG. 8,there was also a reaction pathway involving cyclopentanone as an earlyproduct that was subsequently hydrogenated to cyclopentanol and1-pentanol. At the higher temperature of 200° C. 78% of the furfural wasconverted during the heat-up. As shown in FIG. 9, the THF-MeOH remainedthe major product (16%) but the GVL (4%), 14PDO (10%) and MTHF (2%)product slate became more prominent. The 12PDO was slightly moreprominent but the GBL and THF were less so. As seen in FIG. 10, thecyclopentanone product was no longer present but cyclopentanol and1-pentanol remained through the end of the test. At the highertemperature of 250° C. as seen in FIG. 11, 96% of the furfural wasconverted during heat-up. As shown in FIG. 11, the MTHF product becamedominant (27%) along with its intermediates, GVL (22%) and 14PDO. TheTHF-MeOH product was formed initially (34%) but reacted further to a lowof 3% @ 4 h, perhaps to the THF (10%). GBL, which was present early on,was similarly reacted to THF. The cyclopentanone pathway productsrepresented in FIG. 12 was still evident but all three products werereacted further and no longer present by the end of the test, havingprobably broken down to methane. At 300° C. no furfural survived theheat-up period. The THF-MeOH product (10% yield at time 0) was reactedfurther and disappeared after the first sample. MTHF was the majorproduct (38% @ 0.5 h) with THF as the important subsequent product. Thereverse equilibrium product slate highlighted by GVL and levulinicacid¹³ were also significant. The cyclopentanone product was found (12%)at time 0 but was reduced to trace quantities by 1.5 h. The subsequentalcohol products were not found. ^(xiii) Elliott, D. C., & Fyre, J. G.,Jr. (1999) Hydrogenated 5-Carbon Compound and Method of Making. U.S.Pat. No. 5,883,266.

Palladium Catalyzed Hydrogenations. In the case of palladium catalysis,the results were different. At 150° C., the primary product fromguaiacol was 2-methoxycyclohexanone, resulting from a less completesaturation of the phenolic ring while a large portion of the guaiacolremained unreacted. Methoxycyclohexanol was found at only 1/10^(th) theconcentration of the cyclic ketone. Cyclohexanediol was a lesserproduct, and cyclohexanol and phenol were almost insignificant. Themethanol byproduct was found. At 200° C., shown in FIG. 13 themethoxycyclohexanols were the main product, but some cyclohexanediol waspresent. Cyclohexanol was slightly more prominent. More methanol waspresent. As seen in FIG. 14, at 250° C. methoxycyclohexanols were themain product, but significant guaiacol remained at the end of the test.Cyclohexanediol was a minor product. Cyclohexane was a noticeableproduct and slightly surpassed in quantity both cyclohexanol and phenol.Unlike the case of ruthenium catalysis, over the period of the test, thetotal amount of aqueous phase products appeared to remain nearlyconstant. At 300° C. the reaction of guaiacol throughmethoxycyclohexanol to cyclohexane was evident, as seen in FIG. 15.Methanol was the other significant product and became the major aqueousphase product by the end of the test. Phenol also played a larger rolein the conversion process at this higher temperature than at the lowertemperatures. Guaiacol was converted to almost 98% after the 4 hours attemperature. The total amount of aqueous phase products dropped by about¾ths by the end of the test, suggesting that the major products were thevolatile cyclic hydrocarbons.

Acetic acid did not appear to react over palladium catalyst at 200° C.(see FIG. 16) or below. As seen in FIG. 17, at 250° C. there was about a5% yield of ethanol after 4 hours. At 300° C. the yield was increased tonearly 20% with a few percent of ethyl acetate formed as shown in FIG.18. Unlike with ruthenium, there appeared to be little gasification ofthese products even at up to 300° C.

The furfural conversion chemistry was also much different for thepalladium catalyzed case. Furfural reacted quickly at these conditions.It was found only in the initial samples from 150 and 200° C. tests. At150° C. the main product was cyclopentanone. MTHF was present atslightly higher concentration than THF-MeOH. GVL was a lesser butsignificant product. As shown in FIG. 19, the MTHF and THF-MeOH wererecovered from the 200° C. test at about the same concentration as at150° C., but GVL was increased to the second most prevalent product. Atthe higher temperature of 200° C. the cyclopentanone product wasnoticeably converted to cyclopentanol, as seen in FIG. 20. At 250° C.MTHF was the largest product, as seen in FIG. 21. GVL and THF-MeOH werepresent in nearly equal amounts. Levulinic acid showed up early but wasconverted (to GVL) until it was gone by the end of the test. In FIG. 22the transition was obvious from the early production of cyclopentanonewith its subsequent conversion to cyclopentanol and the final product,1-pentanol. At 300° C. (see FIG. 23) the early production of levulinicacid led quickly to GVL and MTHF formation. Similarly GBL and THFformation were significant throughout, though the GBL was gone by theend of the test. As seen in FIG. 24, 1-pentanol was the major productpresent at the end of the test.

The ruthenium catalysis of the aqueous phase reforming and methanationreactions limits its use to less than 250° C. for efficienthydrogenation chemistry. At higher temperature the formation of methaneand carbon dioxide becomes the all-consuming reaction pathway. Sincepalladium does not catalyze the gasification reactions, it can be usedat higher temperatures for hydrogenation.

Because of these differences there are different product slatesachievable with the two catalysts. Acetic acid can not be effectivelyhydrogenated to ethanol with ruthenium. At the temperatures where thereis significant activity, the gasification reactions were driving towarda final product of methane and carbon dioxide. On the other hand, wediscovered, surprisingly, that acetic acid can be effectivelyhydrogenated to ethanol using a palladium catalyst at 300° C.

An important mechanistic route from furfural to cyclopentanone andpentanols was identified. At 250° C. and above with ruthenium catalyst,these products were gasified like the acetic acid and ethanol. Themechanism of furfural hydrogenation to tetrahydrofuran-methanol appearsto be a final product for both ruthenium and palladium catalysis only atlower temperature. The pathway through γ-valerolactone (including someequilibrium-formed levulinic acid) to 1,4-pentanediol andmethyl-tetrahydrofuran was more important at 250° C. and above.

As reported earlier for substituted guaiacols, the hydrogenation pathwayusing ruthenium catalysis passes through methoxycyclohexanol tocyclohexanediols at low temperature and continues on to cyclohexanol athigher temperature. At 250° C. and above the gasification reactionsbecome dominant. In contrast, palladium catalysis leads first tomethoxycyclohexanone at 150° C., methoxycyclohexanol at 200° C. withsome cyclohexanediol. At 250° C. the product slate is shifted towardcyclohexanol and cyclohexane (without gasification), and by 300° C. theproduct slate is shifted strongly to cyclohexane with a large methanolbyproduct.

EXAMPLES

Method for Batch Reactor Tests. A Parr 4562M 450 mL Hastelloy C pressurevessel was used for these reactions. The catalyst (5 g) was placed inthe reactor with hydrogen gas at 4.2 MPa and reduced at 250° C. for 2 h,and then cooled. The catalysts were either a 3 wt % palladium on acarbon granule (12×50 mesh) produced by the incipient wetness method or7.8 wt % ruthenium on carbon extrudates (1.5 mm) produced by Engelhard.A vacuum was drawn on the reactor and the liquid mixture (200 g) of 5 wt%, each of furfural, guaiacol (2-methoxy-phenol), and acetic acid, inwater was pulled into the reactor vessel. The reactor was thenpressurized to 6.9 MPa with hydrogen and heated to desired temperature.The solution was agitated with the turbine paddle stirrer at 1000 rpmthroughout the test. The desired operating pressure of 13.8 MPa was seton the hydrogen gas regulator and maintained throughout the experiment.By this method hydrogen was added to the reactor as it was used in thereactions. For higher temperature tests, in which gasification occurred,the operating pressure went above the regulator setting and therefore nofurther hydrogen was added to the system and the chemistry was thereforehydrogen limited. In a single uncatalyzed test performed at 250° C., asolid, polymeric material formed from the furfural (no furfural wasdetectable at the end of the test) with a residual level of guaiacol andacetic acid in the aqueous phase similar to that in the feedstock.Liquid samples (2 g) were recovered by a sample dip tube at 0, 0.5, 1,1.5, 2, 3, and 4 h. A purge sample was pulled before each collectedsample, in order to make sure the sample lines were clear of residualproduct material. After the time of the test the system was cooled toroom temperature, the residual gas product was vented, and a sampleanalyzed on a Carle series 400 GC. The offgas volume was measuredthrough a wet test meter. Remaining liquid product was weighed alongwith the sample weights to get an over all mass balance.

Method of Product Analysis. Gas chromatography (GC) was performed withan Agilent model 6890 with a flame ionization detector (FID) to analyzethe samples. Samples were run neat, if they were a single phase,typically only the later products. When two or more phases were present,acetone was added (1 mL) to dilute and bring the solution to one phase.The GC parameters included an injection size of 0.2 μL and an injectiontemperature of 260° C.; splitless injection was used. The temperatureprogram started at 30° C. and a 10° C./min ramp to 260°, then held for 5min. A constant flow of 30 cm/sec was used with a starting pressure of16.87 psig. The column used was an Agilent WaxEtr 60 m×320 μm with a 1.0μm film thickness. The detector was set at 275° C. with 40 ml/min H₂ and450 ml/min air. The carrier mode was constant with column and makeupflow combined for 45 ml/min; makeup gas was nitrogen.

Calibration was done with a 3-point calibration using the followingcomponents: phenol, cis-1,2 cyclohexanol, acetic acid,2-methoxycyclohexanol, cyclohexanol, furfural, guaiacol, cyclohexanone,2-butanol, ethanol, tetrahydrofuran, 2-methyl-tetrahydrofuran,cyclohexyl-methyl-ether. The standards were diluted in a 80/20acetone/water solution. Uncalibrated components were given asemi-quantitative value based on similar components having the samenumber of carbon atoms.

Gas chromatography—mass spectrometry was used for qualitative analysisusing an Agilent model 5890 GC running the same temperature programdescribed above and the identical column, coupled with an Agilent model5972 Mass Selective Detector (MSD). The MSD was scanning at a rate of1.6 scans/sec from 20-500 atomic mass units. The mass data was analyzedusing Agilent Chemstation software G1701AA version A02.00. The compoundpeaks were determined using a Probability-Based Matching (PBM)algorithm. Two libraries were used to identify peaks, the Wiley275library (275,000 compounds) and an in house developed library ofcompounds we had determined from previous bio-oil analysis efforts¹⁰. APBM library search proceeds by searching mass spectral libraries usingthe probability-based matching algorithm developed at CornellUniversity. The search algorithm compares an unknown spectrum to eachreference spectrum using the reverse search technique. A reverse searchtechnique verifies that the main peaks in a reference spectrum arepresent in the unknown spectrum.

Pyrolysis Oil Hydrotreating: Process Performance

The apparatus used for hydrotreating bio-oil in a continuous (not abatch) process was a fixed catalytic bed in a tubular reactor operatedwith concurrent down-flow of bio-oil and hydrogen gas. A bench-scaleunit with a 400-milliliter fixed catalyst bed was assembled in our labfor process tests with different feedstocks, catalysts, and processingconditions. The bio-oil was fed to the reactor by a high-pressuremetering piston pump. The pump's feed cylinder, feed lines, and thereactor were all maintained at temperature by a circulating hot oilsystem. Pressure in the reactor was maintained by a dome-loadedback-pressure regulator. Products exiting the reactor were cooled, andthe condensed liquids collected in sampling cylinders, which wereperiodically drained. The gas product was vented through a meter, andintermittent samples were drawn for analysis.

During the tests using the palladium catalysts, the bio-oils were easilyprocessed in the reactor system. The carbon-supported catalyst had 2 wt% palladium and an apparent bulk density of 0.5 g/mL. Processingtemperature set points in the range of 200 to 360° C. were tested. Asignificant exothermic reaction caused the catalyst beds to operate atup to 20° C. higher than the set point.

Process Results

Tests were performed using a white softwood bio-oil obtained fromDynamotive, which during storage had separated into two phases. Thesetests proceeded smoothly with all reactor components functioning asdesigned. The process data are summarized in Table Y. The temperatureswere measured temperatures, not the set point temperatures.

TABLE Y Hydrotreating of Softwood Bio-oil, Heavy Fraction, withEdge-Coated 1.5% Pd/C Catalyst Run Conditions and Results Temperature, °C. 312 313 347 347 379 Pressure, psig 1910 1917 1911 1913 1939 LiquidHourly Space Velocity, 0.22 0.22 0.22 0.22 0.22 L/L/hr Carbon Balance, %94 83 94 92 90 Material Balance, % 96 93 97 97 94 Product Yield, g/g ofdry feed 0.80 0.75 0.75 0.74 0.72 Product Yield (mass balance 0.83 0.810.77 0.76 0.77 normalized) g/g of dry feed H₂ Consumption, L/L bio-oilfeed 156 232 296 237 319 Deoxygenation, % 48.2 52.0 61.3 58.7 65.3 Waterin oil, wt % 4.93 5.44 2.91 2.91 2.16 Aqueous phase carbon, wt % 13.5613.13 10.70 10.40 10.99 Oxygen in dry oil, wt % 16.99 17.61 12.52 14.2812.52 Density of product oil, g/mL 1.122 1.087 1.03 ~1.03 0.946 TotalAcid Number, mg KOH/g oil 42.0 36.5 Note: Product Yield includes: (1)Oil fraction of oil product (water free) (2) Organics in aqueous phase.

1. A product mixture made from a method comprising: providing a bio-oil;providing hydrogen (H2); and reacting the bio-oil and hydrogen over acatalyst at a temperature of more than 200° C.; wherein the catalystcomprises Pd; and producing a liquid oil from the reaction of thebio-oil and hydrogen.
 2. A method of hydrogenation of furfural,guaiacol, or a substituted guaiacol, comprising: providing a liquidcomprising furfural, guaiacol or a substituted guaiacol; providinghydrogen (H2); and reacting the furfural, guaiacol, or a substitutedguaiacol with hydrogen over a catalyst at a temperature of more than200° C.; wherein the catalyst comprises at least 1 weight % Pd; andconverting the furfural, guaiacol or substituted guaiacol to ahydrogenated product.
 3. The method of claim 2 wherein the liquidcomprises guaiacol or a substituted guaiacol; wherein the guaiacol orsubstituted guaiacol is reacted with hydrogen at a temperature of atleast about 250° C., wherein the hydrogenated product comprises2-methoxy-phenol or other cyclohexanol derivatives, and wherein at leastabout 50% of the guaiacol or substituted guaiacols are converted to2-methoxy-phenol or other cyclohexanol derivatives.
 4. The method ofclaim 2 wherein the catalyst consists essentially of Pd disposed on asupport.
 5. The method of claim 2 wherein the liquid comprises furfural;wherein the step of reacting the furfural with hydrogen over a catalystis carried out at a temperature of at least 280° C.; and wherein atleast 5% of the furfural is converted to 1-pentanol.
 6. The method ofclaim 2 wherein the liquid comprises furfural; and wherein at least 6%of the furfural is converted to 2-methyl-tetrahydrofuran.
 7. The methodof claim 6 wherein the step of reacting the furfural with hydrogen overa catalyst is carried out at a temperature of at about 250° C. to about300° C.
 8. The method of claim 2 wherein the catalyst comprises 2 to 5weight % Pd.
 9. The method of claim 2 wherein the catalyst comprises Pdmetal particles dispersed on a support selected from the groupconsisting of carbon, titania, and zirconia.
 10. The method of claim 3wherein about 50% to about 80% of the guaiacol or substituted guaiacolsare converted to 2-methoxy-phenol or other cyclohexanol derivatives. 11.The method of claim 6 wherein at least 90% of the furfural is consumedby the reaction with hydrogen.
 12. The method of claim 3 wherein thecatalyst comprises at least 1 weight % Pd.
 13. The method of claim 12wherein the catalyst comprises Pd metal particles dispersed on a supportselected from the group consisting of carbon, titania, and zirconia. 14.The method of claim 9 wherein the liquid comprises furfural; and whereinat least 6% of the furfural is converted to 2-methyl-tetrahydrofuran.15. The method of claim 2 wherein the furfural, guaiacol or substitutedguaiacol are present in a bio-oil.